S-(1-(1-Cyanoalkylthio)alkyl)phosphorodithioic compounds as pesticides

ABSTRACT

Novel compounds of the formula I ##STR1## wherein R is H, methyl or ethyl, R 1  and R 2  each is methyl or ethyl or together with the carbon atom to which they are attached form a cyclopropyl group; and R 3  and R 4   each is alkyl, alkoxy or mono- or dialkylamino, are useful as pesticides, particularly against soil insects.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novelS-(1-(1-cyanoalkylthio)alkyl)phosphorodithioic compounds, their use aspesticides and to pesticidal compositions containing these novelcompounds.

2. Description of the Prior Art

Some cyano substituted phosphoric, phosphonic and phosphinic esters areknown broadly as pesticides. U.S. Pat. No. 2,908,604 disclosesS-(cyanoalkoxyalkyl)phosphorothioates as systemic insecticides. GermanPat. No. 1,196,188, Japanese patent application No. 50/69,237 andRussian Pat. No. 227,323 disclose various cyanoethylthioalkyl phosphorusesters useful as insecticides and sometimes other pests, such as mites.

Applicant has discovered new S-(1-(1-cyanoalkylthio)alkylphosphorodithioic compounds having high pesticidal activity, whichcompounds were not known in the prior art.

SUMMARY OF THE INVENTION

The present invention is directed to novel compounds of the formula I##STR2## wherein R is hydrogen atom, a methyl group or an ethyl group;R¹ and R² each independently is a methyl group or an ethyl group or R¹and R² together with the carbon atom to which they are attached form acyclopropyl group; and R³ and R⁴ each independently is an alkyl group,an alkoxy group or a mono- or dialkylamino group, the alkyl portion ofeach group containing from 1 to 4 carbon atoms. The compounds are usefulas pesticides, particularly against soil insects.

Non-limiting examples of species within the scope of the inventioninclude:

S-(1-(1-cyanocyclopropylthio)ethyl O-ethylN-isopropylphosphoramidodithioate,

S-(1-(1-cyano-1-ethylpropylthio)ethyl O,O-diethyl phosphorodithioate,

S-(1-(1-cyano-1-methylethylthio)ethyl 0-ethylN,N-diethylphosphoramidodithioate.

In the compounds of formula I, preferably R is a methyl group or anethyl group. In one embodiment of the invention R is a methyl group.

In the compounds of formula I, preferably R¹ and R² each independentlyis a methyl group or an ethyl group. In one embodiment, R¹ and R² eachis a methyl group.

In the compounds of formula I, preferably R³ and R⁴ each independentlyis an alkoxy group containing 1 to 2 carbon atoms. In one embodiment, R³and R⁴ each is an ethyl group.

In another embodiment of these esters of the invention, R is preferablya hydrogen atom, especially when R¹ and R² are methyl groups.

The S-(1-(1-cyanoalkylthio)alkyl phosphorodithioic compounds of formulaI of the present invention are prepared by forming intermediatealpha-cyano thioethers of formula II below ##STR3## wherein R is ahydrogen atom, a methyl group or an ethyl group and R¹ and R² each is amethyl group or an ethyl group or R¹ and R² when taken together with thecarbon atom to which they are attached form a cyclopropyl group, suchthat R, R¹ and R² correspond to those substituents desired in thecompounds of formula I of the invention. The cyano thioetherintermediates of formula II are chlorinated at the position alpha to thesulfur atom using conventional chlorinating agents, such asN-chlorosuccinimide, e.g. as taught in Ono, N. et al., Synthesis, page1003 (1981) or sulfuryl chloride, e.g. as taught in Truce, W. E. et al.,J. Amer. Chem. Soc., 74, page 3594 (1952). The resulting cyanoalpha-chlorothioethers are then treated with a salt of a dithioic acid(phosphoric or phosphonic). When R³ is alkoxy and R⁴ is mono- ordialkylamino, the corresponding O-alkyl phosphorodichlorothionate istreated sequentially with a mono- or dialkylamine, followed by alkalinehydrogen sulfide.

The alpha-cyano thioether intermediates of formula II are known kinds ofcompounds and are prepared by conventional techniques. In onerepresentative method, for example, an alkylacetonitrile, in which thealkyl groups correspond to R¹ and R² in formula I or II, is treated withlithium dialkylamide at low temperature in an inert solvent, such astetrahydrofuran, and the resulting intermediate is treated with adialkyl disulfide in which the alkyl groups correspond to R in formula Ior II. In another representative method, the same alkylacetonitrilestarting material as above is treated with N-bromosuccinimide in aninert solvent, such as carbon tetrachloride, and the resultingbrominated intermediate is treated with a sodium alkyl sulfide in whichthe alkyl portion corresponds to R in formula I or II, an inert solvent,such as dimethylformamide.

The compounds of the invention have exhibited pesticidal, particularlyinsecticidal, activity. For application, they are generally applied mosteffectively by formulating them with a suitable inert carrier orsurface-active agent, or both. The invention therefore provides apesticidal composition which comprises as active ingredient a compoundof Formula I, together with an inert carrier or surface-active agent, orboth. The invention also provides a method of combatting pests at alocus, which comprises applying to that locus a compound of Formula I ora pesticidal composition according to the invention.

The term "carrier" as used herein means an inert or fluid material,which may be inorganic or organic and of synthetic or natural origin,with which the active compound is mixed or formulated to facilitate itsapplication to the plant, seed, soil or other object to be treated, orits storage, transport and/or handling. Any of the materials customarilyemployed in formulating pesticides, herbicides, or fungicides, aresuitable.

Suitable solid carriers are natural and synthetic clays and silicates,for example, natural silicas such as diatomaceous earths; magnesiumsilicates, for example, talcs; magnesium aluminum silicates, forexample, attapulgites and vermiculites; aluminum silicates, for example,kaolinites, montmorillonites and micas; calcium carbonate; calciumsulfate; synthetic hydrated silicon oxides and synthetic calcium oraluminum silicates; elements such as, for example, carbon and sulfur;natural and synthetic resins such as, for example, coumarone resins,polyvinyl chloride and styrene polymers and copolymers; bitumen; waxessuch as, for example, beeswax, paraffin wax, and chlorinated mineralwaxes; solid fertilizers, for example, superphosphates; and ground,naturally-occurring, fibrous materials, such as ground corncobs.

Examples of suitable fluid carriers are water, alcohols such as, forexample, isopropyl alcohol, glycols; ketones such as, for example,acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, andcyclohexanone; ethers such as, for example, cellosolves; aromatichydrocarbons such as, for example, benzene, toluene and xylene;petroleum fractions such as, for example, kerosene, light mineral oils;chlorinated hydrocarbons such as, for example, carbon tetrachloride,perchloroethylene, trichloroethane, including liquefied, normallyvaporous, gaseous compounds. Mixtures of different liquids are oftensuitable.

The surface-active agent may be an emulsifying agent or a dispersingagent or a wetting agent; it may be nonionic or ionic. Any of thesurface-active agents usually applied in formulating herbicides orinsecticides may be used. Examples of suitable surface-active agents arethe sodium or calcium salts of polyacrylic acids and lignin sulfonicacids; the condensation products of fatty acids or aliphatic amines oramides containing at least 12 carbon atoms in the molecule with ethyleneoxide and/propylene oxide; fatty acid esters of glycerol, sorbitan,sucrose or pentaerythritol; condensates of these with ethylene oxideand/or propylene oxide; condensation products of fatty alcohols or alkylphenols, for example, p-octylphenol or p-octylcresol, with ethyleneoxide and/or propylene oxide; sulfates or sulfonates of thesecondensation products, alkali or alkaline earth metal salts, preferablysodium salts, or sulfuric or sulfonic acid esters containing at least 10carbon atoms in the molecule, for example, sodium lauryl sulfate, sodiumsecondary alkyl sulfates, sodium salts of sulfonated castor oil, andsodium alkyl-aryl sulfonates such as sodium dodecylbenzene sulfonate;and polymers or ethylene oxide and copolymers of ethylene oxide andpropylene oxides.

The compositions of the invention may be prepared as wettable powders,dusts, granules, solutions, emulsifiable concentrates, emulsions,suspension concentrates and aerosols. Wettable powders are usuallycompounded to contain 25, 50 or 75% by weight of the active compound andusually contain, in addition to the solid carrier, 3-10% by weight of adispersing agent, 15% of a surface-active agent and, where necessary,0-10% by weight of stabilizer(s) and/or other additives such aspenetrants or stickers. Dusts are usually formulated as a dustconcentrate having a similar composition to that of a wettable powderbut without a dispersant or surface-active agent, and are diluted in thefield with further solid carrier to give a composition usuallycontaining 0.5-10% by weight of the active compound. Granules areusually prepared to have a size between 10 and 100 BS mesh (1.676-0.152mm), and may be manufactured by agglomeration or impregnationtechniques. Generally, granules will contain 0.5-25% by weight of theactive compound, 0-1% by weight of additives such as stabilizers, slowrelease modifiers and binding agents. Emulsifiable concentrates usuallycontain, in addition to the solvent and, when necessary, cosolvent,10-50% weight per volume of the active compound, 2-20% weight per volumeemulsifiers and 0-20% weight per volume of appropriate additives such asstabilizers, penetrants and corrosion inhibitors. Suspensionconcentrates are compounded so as to obtain a stable, non-sedimenting,flowable product and usually contain 10-75% weight of the activecompound, 0.5-5% weight of dispersing agents, 1-5% of surface-activeagent, 0.1-10% weight of suspending agents, such as defoamers, corrosioninhibitors, stabilizers, penetrants and stickers, and as carrier, wateror an organic liquid in which the active compound is substantiallyinsoluble; certain organic solids or inorganic salts may be dissolved inthe carrier to assist in preventing sedimentation or as antifreezeagents for water.

Aqueous dispersions and emulsions, for example, compositions obtained bydiluting a wettable powder or a concentrate according to the inventionwith water, also lie within the scope of the present invention. The saidemulsions may be of the water-in-oil or of the oil-in-water type, andmay have a thick, mayonnaise-like consistency.

The compositions of the invention may also contain other ingredients,for example, other compounds possessing pesticidal, especiallyinsecticidal, acaricidal, herbicidal or fungicidal properties, as areappropriate to the intended purpose.

The method of applying a compound of this invention to control pests,e.g. insects or mites, comprises applying the compound, ordinarily in acomposition of one of the aforementioned types, to a locus or area to beprotected from the pests, such as the foilage and/or the fruit ofplants. The compound, of course, is applied in an amount sufficient toeffect the desired action. This dosage is dependent upon many factors,including the carrier employed, the method and conditions of theapplication, whether the formulation is present at the locus in the formof an aerosol, or as a film, or as discrete particles, the thickness offilm or size of particles, and the like. Proper consideration andresolution of these factors to provide the necessary dosage of theactive compound at the locus to be protected are within the skill ofthose versed in the art. In general, however, the effective dosage ofthe compound of this invention at the locus to be protected--i.e., thedosage which the insect contacts--is of the order of 0.001 to 0.5% basedon the total weight of the formulation, though under some circumstancesthe effective concentration will be as little as 0.0001% or as much as2%, on the same basis.

In one embodiment of the invention, the compounds of the invention,particularly when R is a methyl group, are useful for control of insectpests and their larvae in the soil, which are damaging to plants and themethod of such control comprises applying to the soil containing saidpests or to their larvae an effective amount of a compound of formula Iof the invention.

The compounds of formula I of the invention are useful for controlling avariety of insects in the soil which are damaging to growing plants. Thecompounds of the invention are well suited for the control of Diabroticaspecies, for example, Diabrotica virgifera LeConte, Diabroticalongicornis (Say), and Diabrotica undecimpunctata howardi Barber, thewestern, northern and southern corn rootworm, respectively, particularlyin their larval stages. Because the compounds of the invention haveunusually good larvicidal activity, they may be advantageously usedagainst rootworms, cutworms and wireworms, for example, larvae ofDiabrotica (rootworms), Agrotis, Crymodes, Amathes, Euxoa, Peridroma,Lacinipolia, Nephelodes, Actebia, Feltia, Loxagrotis, (cutworms),Agriotes, Limonius, Horiatonotus, Ctenicera, Conoderus (wireworms) andthe like. Some of the better known larval species of the above are:Agrotis ipsilon (Hufnagel) (black cutworm), Agriotes mancus (Say) (wheatwireworm) and particularly the three Diabrotica species mentioned above.

For use as soil insecticides, the compounds of the invention aresuitably applied to the soil at a rate of from about 0.1 to about 10kg/ha. Good control of soil inhabiting insects or their larvae isobtained at rates of from about 0.1 to about 5 kg/ha, and especiallyfrom about 0.1 to about 4 kg/ha. The compounds of the invention canconveniently be formulated for use as granules or powders containing asolid diluent, inpregnated with the compound of the invention. Suchformulations usually contain from about 1 to about 50% by weight of thecompound of the invention. More effective control results when theformulation is physically lightly mixed with the topsoil. The mixing ispreceded or immediately followed by planting seeds which germinate intoplants. The compounds of the invention can also be applied as a drench,that is as a solution or dispersion of compounds of the invention innon-phytotoxic solvent or liquid diluent, suitably water. Such drenchescan be prepared by diluting with water a concentrate containing thecompounds of the invention, an emulsifying agent, and preferably anorganic solvent, such as toluene. The compounds of the invention can beapplied as a band, furrow or side dress, either incorporated or not.

ILLUSTRATIVE EMBODIMENTS

The invention is illustrated by the following embodiments, whichdescribe the preparation of typical species of the invention. Theembodiments are for the purpose of illustration and should not beregarded as limiting the invention in any way. The identity of theproducts, including intermediates, was confirmed by elemental, infraredor nuclear magnetic resonance spectral (NMR) analyses as necessary.

EMBODIMENT 1 2-(Ethylthio)-2-methylpropanenitrile

To 3.6 g of sodium hydride (7.2 g of a 50% dispersion washed withhexane) suspended in 50 ml of dimethylformamide was added a solution of17.5 g of ethyl mercaptan in 5 ml of dimethylformamide. The reactionmixture was stirred for 20 min at ambient temperature and then 22.2 g of2-bromo-2-methylpropanenitrile (P. Couveur and A. Bruylants, J. Org.Chem., 18, pages 501-6 (1953)) in 10 ml of dimethylformamide was addedwhile maintaining the temperature below 34° C. The reaction mixture wasstirred at ambient temperature for 2.5 hours, allowed to standovernight, then poured into water and extracted with hexane. The extractwas dried over MgSO₄, the solvent was removed and the residue was vacuumdistilled to give 3.4 g of product, b.p. 95° C. (35 mm).

EMBODIMENT 2 2-(1-Chloroethylthio)-2-methylpropanenitrile

In 10 ml of carbon tetrachloride were placed 1.4 g of2-(ethylthio)-2-methylpropanenitrile and 1.5 g of N-chlorosuccinimideand the mixture was refluxed with stirring for four hours. Solid wasfiltered and the filtrate was evaporated to give 1.8 g of product as ayellow liquid. This product was used without purification.

EMBODIMENT 3 O,O-DiethylS-(1-(1-Cyano-1-methylethylthio)ethyl)Phosphorodithioate

To 15 ml of acetonitrile were added successively 2.24 g of O,O-diethylammonium phosphorodithioate and 1.8 g of the above2-(1-chloroethylthio)-2-methylpropanenitrile. The reaction mixture wasstirred overnight at ambient temperature, poured into water, andextracted with hexane. The hexane solution was washed with aqueoussodium bicarbonate and then dried (MgSO₄). Removal of the solvent gave3.0 g of a yellow oil, which was chromatographed over silica gel toyield 0.6 g of product.

EMBODIMENT 4 O,O-DiethylS-(1-(1-Cyano-1-methylethylthio)propyl)Phosphorodithioate

Following procedures similar to those described in Embodiments 1 through3 above, the desired product was prepared by treating2-bromo-2-methylpropanenitrile with n-propyl mercaptan,alpha-chlorination of the resulting product, and then reaction withO,O-diethyl ammonium phosphorodithioate.

EMBODIMENT 5 O,O-DiethylS-(1-(1-cyano-1-methylethylthio)methyl)Phosphorodithioate

Following procedures similar to those described in Embodiments 1 through3 above, the product was prepared by treating2-bromo-2-methylpropanenitrile with methyl mercaptan, alpha-chlorinationof the resulting product, and then reaction with O,O-diethyl ammoniumphosphorodithioate.

EMBODIMENT 6 2-(Ethylthio)-2-methylbutanenitrile

In 300 ml of tetrahydrofuran under nitrogen was placed 81 ml of 10%lithium diisopropylamide in hexane. The mixture was then cooled to -70°C. and 6.7 g of 2-methylbutaneitrile was added. The reaction mixture wasstirred and maintained at this temperature for 1 hour and then 9.9 g ofdiethyl disulfide was slowly added. After 30 minutes, the reactionmixture was allowed to warm to room temperature. A solid was filteredthrough celite and the filtrate was evaporated. The resulting residuewas dissolved in methylene chloride, washed with water, and dried overNaSO₄. Solvent removal gave 6.9 g of the desired product, b.p. 62°-65°C. (0.85 mm).

EMBODIMENT 7 2-(1-Chloroethyl)-2-methylbutanenitrile

In 150 ml of dichloromethane was placed 4.3 g of2-(ethylthio)-2-methylbutaneitrile. After cooling to 10° C., 4.05 g ofsulfuryl chloride was added dropwise. The reaction mixture was stirredat room temperature overnight. The solvent was removed to give 5.33 g ofproduct, which was used without purification.

EMBODIMENT 8 O,O-DiethylS-(1-(1-Cyano-1-methylpropylthio)ethyl)Phosphorodithioate

In 50 ml of dichloromethane were placed 5.59 g of O,O-diethyl hydrogenphosphorodithioate and 3.18 g of sodium carbonate. This mixture wasstirred at room temperature for 45 minutes and then 5.33 g of2-(1-chloroethyl)-2-methylbutanenitrile was added. After stirring for 3days at room temperature, the reaction mixture was washed successivelywith 1M sodium bicarbonate and water, dried (MgSO₄) and distilled underreduced pressure to give 6.9 g of product, b.p. 135°-140° C. (0.05 mm).

EMBODIMENT 9 O,O-DiethylS-(1-(1-Cyano-1-cyclopropylmethylthio)ethyl)Phosphorodithioate

Following procedures similar to those described in Embodiments 6 through8 above, the desired product was prepared by treatingcyclopropanecarbonitrile with lithium diisopropylamide followed bydiethyl disulfide, treating with sulfuryl chloride, and then treatingthe resulting product with O,O-diethyl sodium phosphorodithioate.

EMBODIMENT 10 Pesticidal Activity

Activity of the compounds of this invention with respect to insect andacarine pests determined by using test methods to test the toxicity ofthe compounds is as follows:

I. Houseflies (Musca domestica (Linne)) were tested by placing 505-day-old houseflies into a spray cage and spraying with 0.6 ml of asolution of test compound. After spraying, the flies were anesthetizedwith CO₂ and transferred to a recovery cage containing a milk pad forfood. The cages were held for 18-20 hours after which mortality countswere made. Both dead and moribund were counted. The tests were conductedemploying several different dosage rates of each test compound.

II. Pea aphids (Acyrthosiphon pisum (Harris)) were tested by placingabout 100 aphids on broad bean plants. The plants were sprayed withdilutions of acetone solution of test compound into water containing anemulsifier and held in containers under laboratory conditions for 18 to20 hours at which time the living aphids in the containers were counted.The tests were conducted employing several different dosage rates ofeach test compound.

III. Adult female two-spotted spider mites (Tetranychus urticae (Koch))were tested by placing 50-75 mites on the bottom side of leaves of pintobean plants. The leaves were sprayed with dilutions of acetone solutionof test compound into water containing an emulsifier and kept underlaboratory conditions for about 20 hours at which time mortality countswere made. The tests were conducted employing several different dosagerates of test compounds.

IV. Corn earworm larvae (Heliothis zea (Boddie)) were tested by sprayinga broad bean plant with dilutions of acetone solution of test compoundinto water containing an emulsifier. Immediately after spraying, 5larvae were transferred to the plant and held for 44-46 hours, at whichtime the dead and moribund larvae were counted. The tests were conductedemploying several different dosage rates for each test compound.

In each instance, the toxicity of the compound of the invention wascompared to that of a standard pesticide (Parathion), its relativetoxicity then being expressed in terms of the relationship between theamount of compound of the invention and the amount of the standardpesticide required to produce the same percentage (50) of mortality inthe test insect or acarine. By assigning the standard pesticide anarbitrary rating of 100, the toxicities of the compounds of theinvention were expressed in terms of the toxicity indices, whichcompares the toxicity of the compounds of the invention with that of thestandard pesticide. That is to say, a test compound having a ToxicityIndex of 50 would be half as active, while one having a Toxicity Indexof 200 would be twice as active as the standard pesticide. The ToxicityIndices are set forth in Table I.

                  TABLE I                                                         ______________________________________                                        PESTICIDAL ACTIVITY EXPRESSED AS TOXICITY                                     INDEX RELATIVE TO THAT OF PARATHION AS A                                      STANDARD EQUAL TO 100                                                         Embodi-                             Two-Spotted                               ment   Housefly Pea Aphid Corn Earworm                                                                            Spider Mite                               ______________________________________                                        5      56       1750      16        3192                                      3      13       66        16        496                                       4      7.5      56        4.8       438                                       8      12       32        6.4       106                                       9      16       318       12        1708                                      ______________________________________                                    

EMBODIMENT 11 Soil Activity

The test chemical is dissolved in a solvent and thoroughly incorporatedinto dry soil. After venting traces of solvent, the soil moisture levelis brought to 9% by adding water and thoroughly mixed.

Sixty grams of the moist soil is added to a 4 oz wide-mouthed jar to 1/2full. Two sweet corn seeds, which have been surface sterilized in 0.2%sodium hypochlorite solution for 15 minutes and rinsed with water, arepressed into the soil near the perimeter of the jar. A small cavity ofabout 2.5 cc is opened in the surface of the soil and 20 Diabroticaundecimpunctata undecimpunctata Mannerheim (western spotted cucumberbeetle) eggs are placed in the well. They are immediately covered overwith fine-seived Zonolite or Vermiculite and the covering material iswetted with about 1.5 cc of water. The jar is then capped with a lidinto which two 2 mm holes have been drilled for ventilation. The jarsare held under lamps at 27° C. The eggs are generally two to four daysold.

After one week, the jar contents are examined for the presence of livelarvaee their number is recorded and the corn roots are examined forfeeding damage. Compounds showing control at 3 ppm or lower rate in thefirst week are evaluated at subsequent weeks. Activity at 3 ppmindicates useful soil insecticidal activity.

Results of these tests were evaluated and reported as follows:

    ______________________________________                                        Rating    Complete Potential                                                                          Larval Count                                          ______________________________________                                        0         Complete control                                                                            0                                                     1         Excellent     >0 to ≦3                                       2         Good          >3 to ≦6                                       3         Fair           >6 to ≦10                                     4         Poor          >10                                                   ______________________________________                                    

Specific results of tests with compounds of the present invention areshown in Table II below.

                  TABLE II                                                        ______________________________________                                        CONTROL OF DIABROTICA UNDECEMPUNCTATA                                         UNDECEMPUNCTATA LARVAE IN SOIL                                                         dosage Rate                                                                              Weeks after Treatment                                     Embodiment (ppm)        0     2     4   8                                     ______________________________________                                        5          3.0          0     0     4   --                                               1.0          0     4     --  --                                               0.3          0     4     --  --                                               0.1          4     3     --  --                                    3          3.0          0     0     0   0                                                1.0          0     0     0   0                                                0.3          0     0     1   4                                                0.1          1     1     4   4                                     4          3.0          0     0     0   0                                                1.0          0     0     1   3                                                0.3          3     4     --  --                                               0.1          3     --    --  --                                    8          3.0          0     0     0   0                                                1.0          0     0     0   0                                                0.3          0     4     1   4                                                0.1          4     4     3   --                                    9          3.0          0     0     0   0                                                1.0          0     0     1   1                                                0.3          1     3     4   --                                               0.1          3     4     3   --                                    ______________________________________                                    

What is claimed is:
 1. A compound of the formula I ##STR4## wherein r isa methyl group or an ethyl group; R¹ and R² each independently is amethyl group or an ethyl group; or R¹ and R² together with the carbonatom to which they are attached form a cyclopropyl group; and R³ and R⁴each independently is an alkoxy group containing from 1 to 4 carbonatoms.
 2. A method for combating pests at a locus, which comprisesapplying to the locus or the pests, a pesticidally-effective amount of acompound according to claim
 1. 3. A compound according to claim 1wherein R³ and R⁴ each independently is an alkoxy group containing 1 to2 carbon atoms.
 4. A compound according to claim 3 wherein R³ and R⁴each is an ethyl group.
 5. A compound according to claim 4 wherein R, R¹and R² each independently is a methyl group or an ethyl group.
 6. Acompound according to claim 5 wherein R is a methyl group.
 7. A compoundaccording to claim 6 wherein R¹ and R² each is a methyl group.
 8. Amethod according to claim 2 wherein the pests are insects or mites.
 9. Amethod according to claim 2 wherein the pests are insects or theirlarvae in the soil, which are damaging to plants.
 10. A method accordingto claim 9 wherein the insect pests or their larvae are from the speciesDiabrotica.
 11. A pesticidal composition comprises a pesticidallyeffective amount of a compound according to claim 1 and at least onecarrier or surface-active agent.